Motor housing with integrally molded electric connector

ABSTRACT

A motor housing structure with an integrally molded electric connector comprises a front flange (26) and a molded rear housing (28) fixed respectively to the front and rear ends of the core (12) of the stator (10) of a motor, and supports a rotor (20) for rotation in rotary bearings (30, 32) held respectively on the front flange (26) and the molded rear housing (28) with a gap between the inner circumference of the stator (10) and the outer circumference of the rotor (20). The front flange (26) is formed of a metal and the rear housing (28) is formed as a lightweight resin member, by molding. An electric connector unit (40), to which an external electric connector (50) is connected to supply electric drive current to the motor, is formed integrally with the molded rear housing (28). The external electric connector (50) is plugged into the electric connector unit (40) in a direction along the axis of the motor, to electrically connect the external electric connector (50) to the electric connector unit (40).

TECHNICAL FIELD

The present invention relates to an industrial motor for use as arotative drive source for driving a machine tool or the like and, moreparticularly, to a housing structure for a motor having a portion formedby molding a resin and integrally provided with a primary portion of anelectric connector to enable a supply of an electric drive current tothe motor.

BACKGROUND ART

An industrial motor widely used as a rotative drive source for machinetools and other industrial machines has a construction including alaminated stator core with an outer circumference serving as the casingfor the motor, a stator formed by inserting excitation coils in thelaminated stator core, a front housing joined to the front end of thelaminated stator core, a rear housing joined to the rear end of thelaminated stator core, rotary bearings fitted in holes in the front andrear housings, and a rotor supported for rotation in the rotary bearingswithin the bore of the stator, with a gap between the outercircumference of the rotor and the inner circumference of the stator.

Such an industrial motor is formed, by taking into consideration thatthe industrial motor is mostly subjected to severe running conditionsdue to a continuous long operation thereof, in a construction havingsufficient mechanical strength by forming the principal components frommetal, particularly, the front and rear housings joined respectively tothe front and rear ends of the stator core, in addition a means fortransmitting and dispersing heat generated by copper loss and iron losswhen an electric drive current is supplied to the exciting coils isincorporated to thereby prevent damage to and a reduction in the life ofthe motor due to an increase in the temperature of the motor to a highlevel. A motor having a greater output generates a greater amount ofheat, and thus a metallic housing having a high heat conductivity isessential to a large-capacity industrial motor, so as to prevent burningthe excitation coils. On the other hand; power, i.e., the excitationcurrent, is supplied to an industrial motor having such a metallichousing, in, most cases, by electrically connecting an electricalconnector (for example, a male electric connector) at the extremity of apower supply cable to a female electric connector screwed to a connectorbase projecting outward from a portion of the metallic rear housing ofthe motor.

FIG. 4 shows an example industrial motor provided with a conventionalhousing structure. This conventional industrial motor is constructed byjoining a metallic front flange 3 and a rear housing 4 respectively tothe front and rear ends of the core 2 of a stator 1, disposing a rotor(not shown) inside the stator 1 with its output shaft 5 projecting tothe front from the front flange 3 so as to be connected mechanically toa driven member by a coupling or the like, and joining a cover 6 to therear end of the rear housing 4 so as to cover the rear end of the motor.A connector base 7 is formed on the rear housing 4 so as to protruderadially outward from the outer circumference of the rear housing 4. Anoff-the-shelf electrical connector 8 is fastened to the connector base 7by screws 9.

Such a construction provided with the electrical connector screwed tothe connector base of the metallic housing requires a process forattaching the electrical connector 8 to the connector base 7 usingscrews 9 by hand during the fabrication of the motor.

Furthermore, when the motor is intended for use as the rotative drivesource of a machine tool, a packing 9' is placed between the electricconnector 8 and the connector base 7 to prevent wetting the interior ofthe motor with machining liquid splashed out during the operation of themachine tool. The electrical connector 8 is fastened to the connectorbase 7 by the screws 8, and then the junction of the electric connector8 and the connector base 7 is coated with a sealing grease to preventmoisture leakage into the motor. Thus, the motor manufacturing processrequires an excessive amount of work, which is an impediment to anydesired cost reduction.

Furthermore, although the construction having the connector base 7projecting from the outer circumference of the metallic rear housing 4is intended to reduce costs through the employment of the availableelectrical connector 8, the connector base 7 radially projecting fromthe outer circumference of the housing increases the overall size of theenveloping surface of the motor including the top of the connector base7. Thus, the motor requires a relatively large space for installation ona machine tool or the like.

On the other hand, the conditions for dispersing heat generated bycopper loss and iron loss are not very severe with an industrial motorhaving a comparatively small output capacity. The rear housing need notnecessarily be formed from metal but may be formed from a resin, in viewof forming a motor having a lightweight construction, provided that onlythe front flange is formed from metal, to ensure satisfactory heatconduction and sufficient mechanical strength for supporting the outputshaft and for coupling the output shaft and the driven member.

DISCLOSURE OF THE INVENTION

Accordingly, a principal object of the present invention is to provide amotor housing structure capable of solving the forgoing problems.

Another object of the present invention is to provide an industrialmotor having a construction, including a rear housing formed by moldinga resin and having a portion integrally provided with an electricalconnector incorporated therein by molding.

To achieve the foregoing objects, the present invention provides a motorhousing structure with an integrally molded electrical connector,including a front flange fixed to the front end of the stator core ofthe motor and a rear housing fixed to the rear end of the stator core.The rear housing rotatably support a rotor shaft mounted with the rotorof the motor disposed inside the stator with a gap between thecircumference of the rotor and the inner circumference of the stator,and on rotary bearings held on the front flange and the rear housing.

The front flange is formed from metal and has a front surface from whichthe output shaft of the motor formed in the extremity of the rotor shaftprojects outside to the front.

The rear housing is formed by molding a resin, and is provided in oneportion thereof with a hollow bulge forming an electric connector meansintegrally incorporated in the portion to supply electrical drivecurrent to the motor therethrough.

When molding the thus molded rear housing of the motor housingstructure, the primary portion of the electrical connector is moldedintegrally with the rear housing. Therefore, a locking mechanism forholding an external electrical connector in place and an externalelectrical connector guide groove for guiding the external electricalconnector so that the external electrical connector can be correctlyreceived in the electrical connector means in a given position can bothbe formed when molding the rear housing. Therefore, the motor housingstructure does not need a sealing structure and the work needed forscrewing the component parts of the electric connector can beeliminated.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, features and advantages of the presentinvention will become more apparent from the following description takenin connection with the accompanying drawings, in which:

FIG. 1 is a partially cutaway front elevation of a motor with a moldedhousing having an integrally molded electric connector in a preferredembodiment according to the present invention;

FIG. 2 is a side elevation of the motor shown in FIG. 1;

FIG. 3 is an exploded perspective view of a molded rear housing includedin a motor housing in another embodiment according to the presentinvention; and

FIG. 4 is a partially sectional front elevation of a conventionalindustrial motor and a connector structure incorporated into the sameindustrial motor.

BEST MODE OF CARRYING OUT THE INVENTION

An industrial motor shown in FIG. 1 is a servomotor embodying thepresent invention. The servomotor has a stator 10 and a rotor 20disposed in the central bore of the stator 10 with a gap between theinner circumference of the stator 10 and the outer circumference of therotor 20. The stator 10 incorporates a stator core 12 and excitationcoils 14, and the rotor 20 has a rotor shaft 22 extended in its centralportion thereof. The front end 24 of the rotor shaft 22 is formed as anoutput shaft projecting to the front, and a metallic flange 26 havingthe shape of a bell jar is fastened to the front end of the stator core12 by screw bolts, not shown. A molded resin rear housing 28 formed bymolding a resin is fastened to the rear end of the stator core 12 byscrew bolts. The rotor shaft 22 is supported rotatably in rotarybearings 30 and 32 fitted in the respective central portions of thefront metallic flange 26 and the molded rear housing 28, respectively.This construction enables the rotor 20 to rotate inside the stator 10,and a cover 34 is attached by suitable attaching means, such as screwsor an adhesive, to the rear end of the molded rear housing 28. Arotation detector, not shown, is housed in the cover 34 for detectingthe rotation of the output shaft of the servomotor.

According to the present invention, the molded rear housing 28 is formedof a heat-resistant resin material having a satisfactory moldability andcapable of ensuring a sufficient mechanical strength for moldings, usinga well-known molding process with an injection molding machine. Themolding process is able to form the molded rear housing 28 with a highdegree of accuracy and is able to form an electrical connector unit 40integrally with the molded rear housing 28, whereas the conventionalmetallic rear housing is provided integrally with only a connector base.The electric connector unit 40 incorporates a molded bulge 42 formed inone portion of the molded rear housing 28 and internally defining aconnector socket 42a that has an opening 42b opening in the axialdirection of the motor, conductive pins 46 provided in the connectorreceiving socket 42a and electrically connected to the excitation coils14 of the stator 10, and a separate base wall 48 holding the conductivepins 46.

An external electrical connector 50 schematically illustrated by brokenlines in FIG. 1 is plugged into the connector socket 42a to connect theexternal electrical connector electrically to the conductive pins 46.

The connector socket 42a is defined within the bulge 42 by an upper wall43a, a lower wall 43b and side walls 43d and 43e, and has asubstantially rectangular cross section.

The electrical connector unit 40 integrally formed with the molded rearhousing 28 can be completed by attaching the molded rear housing 28 tothe rear end of the stator core 12 when assembling the motor. A lockingprojection 44 formed on the lower wall 43b to lock the external electricconnector 50 in place and a guide groove 49 formed in the upper wall 43adefining the connector socket 42a so as to guide a projection formed onthe outer surface of the external electric connector 50 together enablethe external electric connector 50 to be firmly plugged into theconnector socket 42a in a correct position relative to the electricconnector unit 40. This prevents wrong connections of the electricalconnector unit 40 and the external electrical connector 50, andconsequently, the conductors of the external electrical connector 50 fordifferent phases can be correctly connected to the correspondingconductors of the electrical connector of the electrical connector unit40 connected to the excitation coils 14 for different phases,respectively, without fail.

Since the external electrical connector 50 can be inserted deeply intothe socket 42a of the electrical connector unit 40, an effectiveinternal water-proof sealing, hitherto obtained by a packing, can beobtained by providing a sealing structure on the inner surface of thesocket 42a and on the outer surface of the external electrical connector50.

The molded rear housing 28 formed of a resin reduces the weight of themotor. The electrical connector unit 40 integrally formed with themolded rear housing 28 and having the socket receiving the externalelectric connector 50 in a direction parallel to the axis of the motorreduces the size of the enveloping surface of the motor, when comparedwith that of the enveloping surface of the conventional motor providedwith the projecting connector base. Thus, the motor can be formed in acompact construction. Accordingly, the motor requires a relatively smallspace for installation when operatively connecting the motor with thedriven unit of a machine tool or the like.

Although the invention has been described as applied to a servomotor,naturally the present invention is not limited thereto in a practicalapplication. When the present invention is embodied in an industrialmotor (for example, an induction motor having a comparatively smalloutput capacity) a bulge having a socket is formed in a portion of therear housing when forming the rear housing by molding a resin, andconductors are fixedly provided in the socket to construct a motorhousing structure having an integrally molded electrical connectorsimilar to that described above.

FIG. 3 is a perspective view of a motor housing structure in anotherembodiment according to the present invention.

A molded rear housing 128 included in the motor housing structure shownin FIG. 3 is provided integrally with a hollow bulge 142 formed inmolding the same. The bulge 142 has an upper wall 143a, a lower wall143b opposite the upper wall 143a, opposite side walls 143d and 143e,and an end wall 143f. The upper wall 143a, the lower wall 143b and theside walls 143d and 143e define a socket 142e extending in a directionalong the axis of the motor and having an opening 142b. An open 145opening into the interior of the molded rear housing 128 is formed inthe inner portion of the lower wall 143b. When assembling the motor, aholding member 148 holding conductive pins 146 is inserted upward in theopening 145 so that an elastic hook 149c formed in the middle portion ofthe upper end of a vertical section 148a of the holding member 148engages a catch 149b formed on the inner surface of the end wall 143f,to hold the holding member 148 in place on the end wall 143f. Theopposite side portions of the vertical section 148c are receivedrespectively in grooves 141 formed in the side walls 143d and 143e (onlyone of the grooves 141 formed in the side wall 143d is shown), and thusthe holding member 148 is secured to the bulge 142. When secured to thebulge 142, the upper surface of a lower horizontal section 148b of theholding member 148 is flush with the upper surface of the lower wall143b of the bulge 142, and a guide groove 149a formed on the uppersurface of the lower horizontal section 148b is aligned with a guidegroove 149 formed on the upper surface of the lower wall 143b. In thisstate, the conductive pins 146 are held horizontally in the socket 142a,so as to be electrically connected to an external electrical connectorwhen the external electrical connector is plugged in the socket 142a.The lower ends 146a of the conductive pins 146 are electricallyconnected to the excitation coils, not shown, of the stator of the motorwithin the molded rear housing 128 by connecting means such as solderingor caulking. A locking projection similar to the locking projection 44of the first embodiment may be formed on the side wall 143d or 143e ofthe bulge 142, by molding.

As will be understood from the foregoing description of the twoembodiment, in accordance with the present invention, a rear housing forindustrial motors including a servomotor is formed by molding a resin.The molded rear housing is integrally provided with an electricalconnector through which an electrical drive current is supplied to themotor. Accordingly, a process for mounting an electrical connector onthe rear housing by screws can be omitted, to thereby reduce the stepsof the motor manufacturing process, enable cost reductions and allow theuse of a locking mechanism, of a protective mechanism to prevent wrongconnection of an external electric connector, and of a water-proofsealing mechanism having improved structual abilities for a functionalimprovement of the structure of the motor.

It should be noted that many modifications and variations of the presentinvention may occur without departing from the scope of the invention asdefined by the appended claims.

We claim:
 1. A motor housing structure with an integrally moldedelectrical connector, comprising:a front flange fixed to a front end ofa core of a stator of a motor, said front flange rotatably supportingvia rotary bearings a rotor shaft that has a rotor of the motor mountedthereon to be positioned inside the stator via a gap extending betweenan outer circumference thereof and an inner circumference of the core ofthe stator; and a rear housing fixed to a rear end of the core, therotary bearings being held by said front flange and said rear housing,wherein said front flange is formed from metal and is provided with afront surface from which an output shaft of the motor positioned in afront end of the rotor shaft is outwardly projected out a front of themotor, and said rear housing includes a molded housing formed by moldinga resin, the molded housing being provided at a portion of said rearhousing with a hollow bulge, and an electrical connector means formed insaid hollow bulge, for supplying an electrical drive current to themotor, the electrical connector means formed integrally with the moldedhousing including wall means for defining a socket that receives anexternal electrical connector, the wall means defining a first openingin a direction along an axis of the output shaft of the motor andoutside an outer peripheral wall of said rear housing, the wall meansfurther defining a second opening between the socket and an interior ofsaid rear housing, and conductive pin means electrically connected tothe stator of the motor, for electrically connecting with an externalelectrical connector through the first opening when the externalelectrical connector is plugged into the socket, said conductive pinmeans having a holding element so as to be operatively insertablethrough the second opening into the socket from the interior of saidrear housing so as to be connectable with the external electricalconnector.
 2. A motor housing structure with an integrally moldedelectrical connector adding to claim 1, wherein the wall means of theelectrical connector means is provided with an upper wall, a lower wallopposite the upper wall, and a pair of mutually facing side walls.
 3. Amotor housing structure with an integrally molded electrical connectoraccording to claim 2, wherein the wall means of the electrical connectormeans is further provided with an innermost holding wall for holding theconductive pin means.
 4. A motor housing structure with an integrallymolded electrical connector according to claim 2, wherein at least oneof the upper or lower walls is provided with a guide groove for guidingthe external electrical connector when the external electrical connectoris plugged into the socket.
 5. A motor housing structure with anintegrally molded electrical connector according to claim 3, wherein theinnermost holding wall is provided with a catch formed integrallytherewith and operatively engageable with an elastic hook formed in theholding element of the conductive pin means.